2 posts in this topic

Here is a simple Cryptography challenge, I'm going to start you guys off with a polyalphabetic cypher, and I'll post a tutorial in a week to show those who don't know how to break it.

Redtg Lqxrwd! Yvin tg awo gyu zino toajvwn bre Ciksaui lmkd, Qd ik if svdejmkdqxg emlrwn ox kjixdafidiass. Lw ekso tzqk oicy lw vy Q'w ggvfk bby lw ekso tzqk ka fejjgcm ks hwkcqllw.

Bzsa ss sv whiwpdm gp bre Nqyovorw kqzpor. Stky sxoov sc to czqxpzo iflwmpsfxmjkjve (lpw evlrwickjve ughrmb), il psc polv albwxg xwj rcxdjmvc wp ywijc.

Eo hsdw ybrej 'cflzoacitvm' myhpwba cuup sc IOS lwvkg, roo tgxo enlqd dpss xidva ks omdv, ixd opg gqvl tm lrm ynw bg lzoac ql?

Cw iesp, lrqc slcxp qc jmal ltktwvl pqvlwz, lrm gaq bzo Sksaacs bosl egbsc ik gge tyoc ngb zopwilol ceymeovds av lrm movm (sd toakb 3) sxl esw i xkkdoj wx ktv tzm vsadafkwc by dwbwbusnw bzo soykqro, ixd xzgw brejm ada k sauhvm walbwb by bjclo nyrum lrm ueq sfyesny qlc aszw! I xkkdoj bzkb wacmk dpss wiksmb ik bzo tonybz yn dhw kqzporlmpd, bre dijqmb tzm lofd if zwvidigv ly bre cmq dpo gjmsdmb czifmm yf jmhsbstawf.

Ovtoq! Wmbwlojwk


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Hint...here is the key: kasiski

Hello Binrev! Glad to see you have learned the Kasiski test, It is an interesting method of cryptanalysis. To make this easy to do Im gonna try to make this as verbose as possible. This is an example of the Vigenere cypher. Also known as le chiffre indechifferable the unbreakable cypher it has held strong for hundreds of years. We have other unbreakable cyphers such as AES today how long until this falls as well and who will be the one to break it?

So yeah this stuff is just blatent filler the way the Kasiski test works is you look for repeated segements in the code at least 3 and use a factor of all the distances to determine the keysize and from there its a simple matter to brute force the key knowing its size A factor that makes this easier is the length of the cyphertext the larger the text in relation to the key the greater chance of repitition

Enjoy! Ouroboros

Edit: Added spoiler.

Edited by Phail_Saph

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